Zhang Hongyuan

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7 years ago.

How to read the data received by Bluetooth

Hi. If I send two characters at a time to Bluetooth, but the getc () function can only read one character at a time, how can I read the data that Bluetooth receives without causing data loss? Thanks.

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Last updated: 17 Sep 2020

1 Answer

Zoltan Hudak
7 years ago.

Hello Zhang,

You could try to setup suitable Rx buffer and receive data in a while loop in main . With NUCLEO-F072RB for example as below:

#include "mbed.h"

#define RX_MAX 10

Serial  pc(USBTX, USBRX);
Serial  bt(PB_6, PA_10);

int main(void) {
    char    rxBuf[RX_MAX];
    int     i = 0;
    bool    rxBufOverflow = false;

    pc.baud(115200);
    bt.baud(115200);
    pc.printf("Ready to receive data over Bluetooth.\r\n\r\n");

    while (1) {
        while (bt.readable()) {
            if (i < RX_MAX)
                rxBuf[i++] = bt.getc();
            else {
                bt.getc();
                rxBufOverflow = true;
            }
        }

        if (i > 0) {
            printf("Data received:");
            for (int j = 0; j < i; j++)
                printf(" 0x%.2x", rxBuf[j]);
            printf("\r\n");
            if (rxBufOverflow) {
                printf("Error: Rx buffer overflow -> Some data lost!\r\n");
                rxBufOverflow = false;
            }
            printf("\r\n");
            i = 0;
        }
    }
}

Or receive data in a while loop using interrupt service routine:

#include "mbed.h"

#define RX_MAX 10

Serial  pc(USBTX, USBRX);
Serial  bt(PB_6, PA_10);
char    rxBuf[RX_MAX];

volatile int   i = 0;
volatile bool  rxBufOverflow = false;
  
void onBluetoothReceived(void) {
    while (bt.readable()) {
        if (i < RX_MAX)
            rxBuf[i++] = bt.getc();
        else {
            bt.getc();
            rxBufOverflow = true;
        }
    }
}

int main(void) {
    pc.baud(115200);
    bt.baud(115200);
    bt.attach(&onBluetoothReceived, Serial::RxIrq);
    pc.printf("Ready to receive data over Bluetooth.\r\n\r\n");

    while (1) {
        if (i > 0) {
            printf("Data received:");
            for (int j = 0; j < i; j++)
                printf(" 0x%.2x", rxBuf[j]);
            printf("\r\n");
            if (rxBufOverflow) {
                printf("Error: Rx buffer overflow -> Some data lost!\r\n");
                rxBufOverflow = false;
            }
            printf("\r\n");
            i = 0;
        }
    }
}

Accepted Answer